a 1000 watt light could possible grow up to 36 plants at once if you did it 1 plant for every square foot. Of course this would be SOG style grow of only main colas. 1k watt light is good for a 6'x6' area. Now if you had a light mover you could double those figures. What is a light mover? exactly what its name implies. its basically a rail that runs over the tops of the plants, the light is attached to a chain or cable and is slowly pulled back and forth along the rail across the tops of the plants. It closely mimics the path of the sun over the course of a sunny day. There are other ways to move the lights, but basically your just moving the light back and forth over the plants so that all the plants receive about the same amount of light. Many grows have the largest densest plants under the middle of the light as that is where the most intense light is, a light mover basically "spreads " it out a bit.